TCP/IP and UDP
The transfer of data across an ethernet network is achieved using a communication protocol called TCP/IP. This stands for Transport Control Protocol / Internet Protocol. (Note that in this instance internet means inter-network not specifically the Internet). The TCP/IP protocol is actually a suite of protocols defined in a number of documents called RFCs or ‘Request for Comment’.
The suite contains a wide range of protocols designed for specific tasks. Art-Net makes use of the TCP/IP protocol called UDP or User Datagram Protocol.
UDP is in fact used by the bulk of streaming protocols including ShowNet and E1.31 (ACN Lite). The protocol is designed for moving bulk data across the network with the minimum of fuss and overhead. It is a fire and forget protocol, meaning that it can just be sent to any network address; it is not necessary to negotiate a connection (as with TCP) first.
Protocols within the TCP/IP suite are often layered. For example, UDP uses the IP protocol for the low level data transfer.
UDP is defined in RFC768.